There are a number of pacing/training pace calculators on the internet - I like and mostly use Jack Daniels ( American trainer en.wikipedia.org/wiki/Jack_... )

He basically proposes 5 different training paces - long, easy, tempo, interval and repitition (in declining order of pace) . It all sounds very technical and I guess it is - but fairly simple to understand. He gives a brief description of each pace and it's training purpose in his calculator . So for example my training paces ( dependent on a 5K race pace of 31 :00 minutes ( and rounded up a bit for convenient memory) are long 8:10 mins per k, easy 7:45, tempo/threshold 6:30, interval 6:00 and repetition 5:40. As an example , yesterday I did a 10 minute easy warmup run to a track - then did 3x400m repeats ( a bit over 2 minutes each) with a 2 minute rest inbetween each. Then another 10 minute cooldown easy run back home . I will slowly build these short repeats up to around 3 minutes each with a 3 minute rest inbetween until I reach around 6-7 repeats - which will give me a total of 21 minutes workout at 5:40 pace. Just once per week at this pace. he also has other suggestions as to typical once per week tempo paced and interval paced workouts - mostly for a max of 20 minutes plus warmup/cooldown. - plus a longrun each week building up to 90 minutes non-stop. An ongoing programme which has no race distance in mind - but which he says will allow people to participate in 5-10k amateur races.

Bazza1234, it's all a bit technical for me! What I am slowly taking on board is the various heart rate zones. I had a very pleasant trot in zone 3 this morning (whereas I assume from the pace that in the past I've probably been pushing too hard too often). My new watch means I will be training more sensibly and hopefully more sustainably (although I haven't had an injury yet). You are obviously a lot further along the line, it'll take a while to understand all the technicalities.

Yes - it is commonly said that amateurs like us - run too hard on our easy/long days and too easy on the days we are supposed to be running hard. We tend to fall into a "comfortable" zone in the middle - which actually holds us back. Fast and hard shortish runs do certain things for us , while long easy slow runs do other things for us. In between is kind of neither of those two training efffects. Simplistic answer though really. Any kind of running benefits us over sitting on the couch

Thanks for posting this information Bazza, very useful, although I am only just beginning to think about the importance of pace and varied training routines. I got myself confused trying to work out my pace per mile instead of km the other day